动态调用web服务

Question

我网上找了个动态动用的例子
using System;using System.IO;using System.Configuration;using System.CodeDom;using System.CodeDom.Compiler;using System.Net;using System.Web.Services;using System.Web.Services.Description;using Microsoft.CSharp;using System.Collections;using System.Reflection; namespace WuYou.NetSignUp{     /// <summary>     /// WebServiceHelper 的摘要说明。     /// </summary>     public class WebServiceHelper     {         private string @namespace = "EnterpriseServerBase.WebService.DynamicWebCalling" ;        //命名空间         private Assembly assembly = null;    //程序集;         private string classname = string.Empty;  //类名称;         private Type t;             //表示类型;         private object obj = null;       //表示实例;         private Boolean isSuccess = false;   //是否创建实例成功;           public WebServiceHelper(string Url,string classname)         {              if(classname == null || classname == string.Empty)                   this.classname = GetWsClassName(Url);              else                   this.classname = classname;               try              {                   //获取WSDL                   WebClient wc                   = new WebClient();                   Stream stream                  = wc.OpenRead(Url+"?WSDL");                   ServiceDescription sd          = ServiceDescription.Read(stream);                   ServiceDescriptionImporter sdi = new ServiceDescriptionImporter();                   sdi.AddServiceDescription(sd,"","");                   CodeNamespace cn                = new CodeNamespace(@namespace);                   stream.Close();                    //生成客户端代理类代码                   CodeCompileUnit ccu             = new CodeCompileUnit();                   ccu.Namespaces.Add(cn);                   sdi.Import(cn ,ccu);                    CSharpCodeProvider csc          = new CSharpCodeProvider();                   ICodeCompiler icc               = csc.CreateCompiler();                                   //设定编译参数                   CompilerParameters cplist       = new CompilerParameters();                   cplist.GenerateExecutable       = false;                   cplist.GenerateInMemory         = true;                   cplist.ReferencedAssemblies.Add("System.dll");                   cplist.ReferencedAssemblies.Add("System.XML.dll");                   cplist.ReferencedAssemblies.Add("System.Web.Services.dll");                   cplist.ReferencedAssemblies.Add("System.Data.dll");                    //编译代理类                   CompilerResults cr = icc.CompileAssemblyFromDom(cplist, ccu);                                      if(true == cr.Errors.HasErrors)                   {                       System.Text.StringBuilder sb = new System.Text.StringBuilder();                       foreach(System.CodeDom.Compiler.CompilerError ce in cr.Errors)                       {                            sb.Append(ce.ToString());                            sb.Append(System.Environment.NewLine);                       }                       throw new Exception(sb.ToString());                   }                                                assembly = cr.CompiledAssembly;              }              catch (System.Exception ex)              {                   throw new Exception(ex.InnerException.Message,new Exception(ex.InnerException.StackTrace));              }         }          private Boolean CreateInstance()         {              try              {                   t = assembly.GetType(@namespace+"."+classname,true,true);                   obj = Activator.CreateInstance(t);                   isSuccess = true;              }              catch (System.Exception e)              {                   throw new Exception(e.Message);              }              return isSuccess;         }          public object InvokeWebService(string methodanme,object[] parms)         {               if(!isSuccess)              {                   CreateInstance();              }               try              {                                System.Reflection.MethodInfo mi = t.GetMethod(methodanme);                    return mi.Invoke(obj,parms);                          }              catch (System.Exception ex)              {                   throw new Exception(ex.InnerException.Message,new Exception(ex.InnerException.StackTrace));              }          }          private string GetWsClassName(string wsUrl)         {              string[] parts = wsUrl.Split('/') ;              string[] pps   = parts[parts.Length-1].Split('.') ;               return pps[0] ;         }     }}然后调用本地的
string url = "http://localhost/DymaticText/Service1.asmx" ;
string[] args=new string[2];
args[0] ="strere";
args[1] = "China" ;
object result = Proxy.InvokeWebService(url ,"HelloWorld " ,args) ;
this.label3.Text = result.ToString() ;
就出现错误"未将对象引用设置到对象的实例"
用网上别人提供的例子就可以测试成功
这是为什么?
谁碰到过这个问题并且解决了的告诉我一下啊

Answer 1

我也写了一个,可以调用, 没发现问题, 如下:
       const string DefaultUrl = "http://192.168.60.27/ServiceDS/Service.asmx?wsdl";
        static Program instance = new Program();        static void Main(string[] args)
        {
            instance.InvokeMethod();
            Console.ReadLine();
        }        void InvokeMethod()
        {
            Assembly proxyAssembly = CreateWSProxy(DefaultUrl);
            Type proxyType = proxyAssembly.GetType("WebServiceProxy.Service");          
            MethodInfo mi = proxyType.GetMethod("xxxMethod");
            PropertyInfo pi = proxyType.GetProperty("Credentials");
            object proxy = Activator.CreateInstance(proxyType);
            pi.SetValue(proxy, CredentialCache.DefaultCredentials, new object[0]);
            Console.WriteLine(mi.Invoke(proxy, new object[] { "xxx" }).ToString());
        }        Assembly CreateWSProxy(string url)
        {
            if (String.IsNullOrEmpty(url))
                return null;            ServiceDescription wsdl = GetWsdl(url);
            CodeNamespace cns = new CodeNamespace("WebServiceProxy");
            ServiceDescriptionImporter sdi = new ServiceDescriptionImporter();
            sdi.AddServiceDescription(wsdl, null, null);
            sdi.ProtocolName = "Soap";
            sdi.Import(cns, null);            CSharpCodeProvider cp = new CSharpCodeProvider();
            StringBuilder sb = new StringBuilder();
            StringWriter sw = new StringWriter(sb);
            cp.GenerateCodeFromNamespace(cns, sw, null);
            string src = sb.ToString();
            sw.Close();
            Console.WriteLine(src);            CompilerParameters cmp = new CompilerParameters();
            cmp.ReferencedAssemblies.Add("System.dll");
            cmp.ReferencedAssemblies.Add("System.Xml.dll");
            cmp.ReferencedAssemblies.Add("System.Web.Services.dll");
            cmp.GenerateExecutable = false;
            cmp.GenerateInMemory = true;
            cmp.IncludeDebugInformation = false;            CompilerResults cr = cp.CompileAssemblyFromSource(cmp, src);            if (cr.Errors.Count > 0)
                throw new Exception(string.Format("Build failed: {0} errors",
                    cr.Errors.Count));
            return cr.CompiledAssembly;
        }        ServiceDescription GetWsdl(string url)
        {
            WebRequest wreq = WebRequest.Create(url);
            wreq.Credentials = CredentialCache.DefaultCredentials;
            WebResponse resp = wreq.GetResponse();
            Stream stream = resp.GetResponseStream();
            StreamReader sr = new StreamReader(stream, System.Text.Encoding.UTF8);
            string desc = sr.ReadToEnd();
            XmlTextReader xtr = new XmlTextReader(new StringReader(desc));            ServiceDescription wsdl = ServiceDescription.Read(xtr);
            xtr.Close();
            sr.Close();
            stream.Close();
            resp.Close();
            return wsdl;
        }